1. Field of the Invention
The present invention relates to a radar for scanning a beam over a predetermined scanning range.
2. Description of the Related Art
A millimeter-wave type of car-mounted radar that varies the beam azimuth over a predetermined scanning range has been developed. This type of radar transmits and receives a detection signal, and scans a beam to detect the azimuth of a target from changes in received signal strength. For example, in Japanese Unexamined Patent Application Publication No. 2000-180532, changes in received signal strength in the azimuthal direction are determined. When the pattern of the changes in the received signal strength includes a chevron, the azimuth at which a peak of the received signal strength occurs is detected as the target azimuth.
However, this detecting method of the target azimuth based on the chevron pattern of the changes in the received signal strength (a signal-strength profile) generated by the beam scanning cannot detect the azimuth of a target that does not produce a chevron in the signal-strength profile. For example, when a target exists at an azimuth of the outermost angle in the scanning angular range of the beam, only one side of a chevron is formed. Moreover, when a target exists outside and adjacent to the outermost angle where the azimuth can be detected in a beam width, only a portion of a chevron is formed in the signal-strength profile. In both cases, however, only a “shadow” of the target located outside the scanning angular range is cast in the scanning angular range, and the position of the peak in the signal-strength profile cannot be detected. As a result, the target azimuth cannot be detected.